Pass the flag -utf8 to openssl to interpret field values as UTF-8.

By default, field values are interpreted as ASCII but UTF-8 would be a
more reasonable default. Without the -utf8 flag, non-ASCII text gets
garbled without warning. ASCII text works fine either way.
Merge pull request #2 from roubert/utf-8

Pass the flag -utf8 to openssl to interpret field values as UTF-8.